The present invention relates to a human tracking method using a color histogram, and more particularly to a human tracking method using a color histogram, which can track a human being using different target color histograms according to poses of the human being when tracking the human being on the basis of a particle filter.
A monitoring system (also called a surveillance system) for sensing whether a certain specific behavior or accident occurs has been considered to be the most important technique from among various technical fields based on human tracking. With increasing development of modern society, the importance of safety of individuals and facilities is becoming higher not only in public spaces but also in personal spaces.
Particularly, as information technology, unmanned technology, automation, and computerization of modern society are rapidly increasing, unexpected problems continuously occur in security, safety and property of each person and business place.
Therefore, many efforts have been made to protect/manage property and safety of each person and business place, and the importance and range of security have been extended to major facilities, public offices, schools, enterprises, and homes, such that the importance of the monitoring system and the necessity of developing the same are rapidly increasing.
In the case of the conventional monitoring system using a closed circuit television (CCTV), a user who serves as an administrator of the security control center must simultaneously observe a plurality of images with the naked eye, such that the monitoring system has many disadvantages in terms of cost or efficiency due to physical and mental limitations of each person. In order to overcome the above-mentioned disadvantages, the monitoring system has been designed to track the position of one person or the positions of unspecified persons within an image sequence captured by a camera through the human tracking technology based on computer vision technology.
A tracking technology based on color information of an image is used as a representative example of the above-mentioned tracking technology. When a specific object contained in the image moves from one position to another position, the above-mentioned image-color based tracking technology discriminates the position of the object contained in the image through color information of the object, such that it can be applied to a variety of application fields, for example, factory automation, robotics, broadcasting, unmanned monitoring systems, security systems, remote conferencing through communication networks, unmanned aerial vehicle control, etc. In addition, considering that a person obtains a large amount of information visually, many more application fields will be realized in the future.
Generally, the object tracking technology receives an image as an input, and minimizes a difference in characteristic value between a target object and an observation model using any one of template matching, gradient descent, and mean shifting, such that it can estimate the object position to be obtained in a next frame using the minimized difference.
However, according to the above-mentioned tracking technology, provided that an object is temporarily covered with other objects or obstacles on the condition that the movement speed of a person is very high or the person moves in irregular directions, the tracking performance or throughput of the above-mentioned tracking technology is rapidly deteriorated. In order to overcome the above-mentioned problems, a multiple-hypotheses-based tracking method has recently been proposed, which diffuses a plurality of particles in the vicinity of an object on the basis of a stochastic model, measures a characteristic value of an observation model at every particle position, and tracks an object using the measured characteristic value.
Through observation of the characteristic values of multiple particles, the multiple-hypotheses-based tracking method establishes a variety of movable positions of the object to be shifted to the next frame according to a variety of hypotheses, and tracks the object, such that it can obtain an accurate tracking result even in the case of temporary overlapping or rapid movement.
The related art of the present invention is disclosed in Korean Patent Registration No. 10-0886323 issued on 4 Mar. 2009, entitled “METHOD AND APPARATUS FOR REALTIME-TRACKING OBJECT USING COLOR HISTOGRAM”.
The human tracking method using the particle filter according to the present invention has robustness against temporary overlapping or covering, complicated background, rapid movement speed, irregular movement direction, etc. In addition, the tracking method using a color histogram as observation characteristic information of the particle filter has robustness against has robustness against illumination variation, and can track a low-resolution object having a small number of characteristic points (features) at a relatively high accuracy.
However, the tracking method based on color histogram information fails to track a target object under the condition that another object having distribution similar to that of the color histogram of the target object appears in the vicinity of the target object, and there may arise a large difference in human color histogram according to individual poses of the human being, such that the accuracy of tracking is deteriorated when human tracking is achieved using a single color histogram.